Poison sent to US Senator

US Capitol police, the FBI and other agencies launched an investigation on Tuesday after the letter was detected during a routine mail inspection at an off-site facility.

"The Senate mail handling facility that services members' DC offices has received mail that tested positive for ricin," Senate Sergeant at Arms, Terrance W. Gainer said in a written statement.

"While we have no indication that there are other suspect mailings, it is imperative to follow all mail handling protocols," Gainer said, urging Senate employees to remain "vigilant in their mail handling processes."

Members of the Senate were briefed on Tuesday evening on the incident during a meeting about the Boston Marathon attacks with FBI Director Robert Mueller and Janet Napolitano, the secretary of Homeland Security. There is currently no evidence to suggest a link between the two incidents.

There was also no indication as to why the letter may have been sent to Senator Wicker, Gainer said.

Investigations underway

The letter in question was reportedly postmarked from Memphis, Tennessee and had no return address. Gainer described the markings on the envelope as "not outwardly suspicious."

All mail to the US Senate has reportedly now been stopped and the Senate mail facility closed while the investigation is underway. Congressional mail has been screened off-site since letters laced with anthrax were sent to Capitol Hill in the wake of the Sept. 11, 2001, attacks on the Pentagon and World Trade Center.

Ricin can prove lethal, even in small quantities, when ingested orally. The poison, found naturally in castor beans, can cause respiratory problems when inhaled.

ccp/jr (AP, Reuters, AFP)